1. Field of the Invention
The present invention relates to improvements and modifications in an optical axis tilting device for laser optical system with a ball joint mechanism.
2. Description of the Related Art
In the prior art, there has been a known rotary laser surveying machine including an optical axis tilting device for laser optical system to set inclination of a laser beam, for example. Such a known optical axis tilting device includes means to control amounts of tilt angle of the optical axis of the laser optical system relative to a horizontal or vertical direction, such as a threaded shaft as a delivery mechanism for delivering a connection portion between the laser optical system and provided with an encoder detecting a rotation rate of the shaft, or a drive motor rotating a threaded shaft and provided with an encoder.
For example, Japanese Laid-open Patent Application Publication No. Hei 6-26861 discloses such an optical axis titling device configured to tilt a laser optical system from horizontal and vertical positions by driving the delivery mechanism.
There is another type of an optical axis tilting device configured to set inclination of the optical axis of the laser optical system by tilting the laser optical system relative to a tilt sensor of the optical axis tilting device which is in a leveled state.
However, these prior art optical axis tilting devices for laser optical system have a problem that since precision of the tilt angle setting for the rotary laser surveying machine depends on precision of the delivery mechanism, a deviation in the tilt angle setting may occur due to accumulated errors and abrasion of a screw portion of the delivery mechanism arising from repetitive movement thereof, deformation of the screw portion over time, or the like. Accordingly, it is hard to maintain a desired tilt precision for the optical axis of the laser optical system.
In view of solving this problem, the applicant of the present invention developed an optical axis tilting device for laser optical system which achieves a desired precision of a set tilt angle relative to a horizontal or vertical direction of the optical axis of the laser optical system even with occurrence of such errors (disclosed in Japanese Laid-open Patent Application Publication No. 2008-70196).
This optical axis tilting device for laser optical system comprises a lens barrel in which a laser optical system is disposed, an optical axis of the laser optical system being a Z axis, an X axis and a Y axis being orthogonal to each other in a plane orthogonal to the Z axis; a tilt frame being tilted in at least one of an X-axis direction and a Y-axis direction and provided with a tilt sensor detecting a horizontal reference position; a tilt mechanism tilting the tilt frame relative to the lens barrel; and a leveling mechanism supporting the lens barrel tiltably and tilting the lens barrel to level the tilt frame so that the tilt sensor detects the horizontal reference position. Further, the tilt mechanism comprises a threaded shaft rotated by a drive motor, a movable member reciprocated by the shaft and engaging with the tilt frame to tilt it relative to the lens barrel, and a position detector detecting a position of the movable member. The optical axis tilting device is configured to compute a tilt angle of the tilt frame relative to the lens barrel according to the position of the movable member detected by the position detector.
Moreover, this optical axis tilting device further comprises a ball joint mechanism to tilt the tilt frame. Advantageously, the ball joint mechanism has a simple structure of a pivot shaft provided on an arm and a conical recess formed in the tilt frame.
This optical axis tilting device for laser optical system can maintain a desired tilt precision relative to a horizontal or vertical direction of the optical axis of the laser optical system even with the above-described errors due to the repetitive movement of the screw portion.
However, there still remain errors in set tilt angles which even this optical axis tilting device cannot eliminate. The inventors of the present invention have found out what causes the errors in tilt angles, that is, a several micron gap occurring partially between a spherical portion of the pivot shaft and an inner circumferential wall of the conical recess when the tilt frame is tilted.